The standard size for AK-47/AKM rifle barrel threads is 14x1mmLH. The standard size for M-16/AR-15 rifle barrel threads is 1/2x28.
So unthreaded barrel semi auto AK rifles imported to the US are going to have barrels that are 14mm/.551" in diameter or barrels that have had the threads turned off leaving the barrel 12.3mm/.480" to 13mm/.512" in diameter.
The 1997-1998 imported Romanian 7.62x39mm rifles,milled receiver MAK-90,milled receiver MAK-91,and Norinco Hunter models never had the barrels threaded so they are 14mm/.551" in diameter.
The 1997-1998 imported Romanian 5.45x39mm rifles and SAR-2 rifles have 12.7mm-12.9mm/.500"-.508" diameter barrels.
Maadi rifles with unthreaded barrels have the barrels theads turned off and vary 12.3mm-13mm/.480"-.512".
I have threaded several Maadi,Romanian CUR-2 5.45x39mm,and SAR-2 rifles that had barrels 12.7mm-12.9mm/.500"-.508" with a 1/2x28 threading kit. Then bought AK-74 style muzzle brakes made for AR-15 rifles.
So unthreaded barrel semi auto AK rifles imported to the US are going to have barrels that are 14mm/.551" in diameter or barrels that have had the threads turned off leaving the barrel 12.3mm/.480" to 13mm/.512" in diameter.
The 1997-1998 imported Romanian 7.62x39mm rifles,milled receiver MAK-90,milled receiver MAK-91,and Norinco Hunter models never had the barrels threaded so they are 14mm/.551" in diameter.
The 1997-1998 imported Romanian 5.45x39mm rifles and SAR-2 rifles have 12.7mm-12.9mm/.500"-.508" diameter barrels.
Maadi rifles with unthreaded barrels have the barrels theads turned off and vary 12.3mm-13mm/.480"-.512".
I have threaded several Maadi,Romanian CUR-2 5.45x39mm,and SAR-2 rifles that had barrels 12.7mm-12.9mm/.500"-.508" with a 1/2x28 threading kit. Then bought AK-74 style muzzle brakes made for AR-15 rifles.
